Method for controlling aurelia spp. blooms in harbors

ABSTRACT

A method for controlling  Aurelia  spp. blooms in harbors includes: designing different sites at equal intervals in an area in spring, collecting ephyrae of  Aurelia  spp. with an I-type trawl net for zooplankton from bottom to surface, determining whether polyps of  Aurelia  spp. inhabit in the vicinity of the sites; seeking large floating substrates that the polyps attach to using scuba diving in the determined habitats of the polyps; dragging the substrates to a shore base and scraping off all organisms attached to bottom surfaces of the substrates in a physical manner, then air drying the substrates for 7 days or more; and applying an antifouling paint on the bottom surfaces of the dried substrates followed by drying, then returning the substrates back to their original sites in the sea to control the bloom of  Aurelia  spp. in the area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from Chinese Patent Application No. CN 201810329953.0, filed on Apr. 13, 2018. The content of the aforementioned application, including any intervening amendments thereto, is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to research and development of controlling the occurrence of marine ecological disasters, and particularly to a method for effectively controlling Aurelia spp. blooms in harbors.

BACKGROUND ART

Aurelia spp., nicknamed “moon jellyfish”, is a widely distributed species of Aurelia, Ulmaridae, Semaeostomeae, Scyphozoa, Cnidaria, usually 10-30 cm in diameter for adults. In recent decades, Aurelia spp. frequently blooms in many coastal harbors and bays around the globe, including Japan, Korea, America and so on, which has posed severe damages to some coastal infrastructures and caused threats to human social security and normal life. For example, high-density aggregations of Aurelia coerulea near a power plant (Qingdao, China) caused the power failure in local areas due to clogging of cooling water intakes in July 2009. Blooms of A. coerulea near Hongyanhe nuclear power plant (China) resulted in the unit shutdowns for a week, thus bringing direct financial loss of up to hundreds of millions yuan in July 2014. Besides, Aurelia spp. competes with fish for the same baits, and even may prey on a lot of fish eggs and larvae, thus mass occurrence of Aurelia spp. would threaten the neritic fishery resource, reduce the recruitments of fishery resources, and cause the exhaustion of fish stock. Therefore, in order to protect the health of marine ecosystem and development of economy near the shore, there is an urgent need to control the Aurelia spp. blooms.

SUMMARY OF THE PRESENT INVENTION

In view of the above problems, the present invention provides a method for controlling an Aurelia spp. bloom in a harbor.

The method for controlling an Aurelia spp. bloom in a harbor comprises the following steps:

1) designing different sites (≤10) at equal intervals in an area in spring, collecting Aurelia spp. ephyrae with an I-type trawl net for zooplankton from bottom to surface, determining whether Aurelia spp. polyps inhabit in the vicinity of the sites;

2) seeking large floating substrates that the polyps attach to using scuba diving in the determined habitats of the polyps;

3) dragging the substrates to a shore base and scraping off all organisms attached to bottom surfaces of the substrates in a physical manner, then air drying the substrates for more than 7 days; and

4) applying an antifouling paint on the bottom surfaces of the dried substrates followed by drying, then returning the substrates back to their original sites in the sea to control the Aurelia spp. bloom in the area.

In step 1), different sites (≤10) are designed at equal intervals in the area in spring (from April to May). The Aurelia spp. ephyrae are collected with the I-type trawl net for zooplankton from bottom to surface to determine whether the Aurelia spp. polyps inhabit in the vicinity of the sites. If the Aurelia spp. ephyrae are found in a certain site, then the polyps habitat near the site; if no ephyrae are found in this area, the area is further expanded till the Aurelia spp. ephyrae are found.

In step 2), the Aurelia spp. polyps are sought using the scuba diving in an area with reduced water flow near the site where the Aurelia spp. ephyrae are found; it is demonstrated that a large number of Aurelia spp. polyps attach upside down to the bottom surfaces of the floating substrates.

In step 3), all organisms attached to the bottom surfaces of the floating substrates with polyps attached thereto are completely scraped off (it is considered as complete removal when no organism on the bottom surfaces is visible to the naked eye) in a physical manner, and then the scraped substrates are dried in the sun for more than 7 days.

In step 4), 2-3 layers of antifouling paint are applied on the bottom surfaces of the substrates, with a paint film of 50-75 μm in thickness. The paint may be a paint with an antifouling property, such as a modified chlorinated rubber antifouling paint.

Further, the method is described as follows.

(1) Seeking Out Aurelia Spp. Ephyrae

Different sites (≤10 sites) are designed at equal intervals in the area in spring (from April to May). The Aurelia spp. ephyrae (1) are collected with the I-type trawl net for zooplankton from bottom to surface to determine whether the Aurelia spp. polyps inhabit in the vicinity of the sites. If the Aurelia spp. ephyrae (1) are found in a certain site, then the polyps habitat near the site; if no ephyrae are found in this area, the area is further expanded till the Aurelia spp. ephyrae are found.

(2) Seeking Out Aurelia Spp. Polyps Using Scuba Diving

The Aurelia spp. polyps (2) are sought using the scuba diving in an area with reduced water flow near the site where Aurelia spp. ephyrae (1) are found. It is demonstrated that a large number of Aurelia spp. polyps attach upside down to the bottom surfaces (3) of the floating substrates. Not all of these substrates are attached with Aurelia spp. polyps, and therefore an on-site search using scuba diving is required for screening of the substrates.

(3) Removing Polyps on the Bottom Surfaces of the Substrates

The floating substrates to which Aurelia spp. polyps attach are dragged to a shore-based plant (e.g., a dockyard), and Aurelia spp. polyps and all of other sessile organisms attaching to the bottom surfaces of the substrates are completely scraped off in a physical manner.

(4) Applying Antifouling Paint on the Bottom Surfaces of the Substrates

The substrates are dried in the sun for more than 7 days after the Aurelia spp. polyps and other sessile organisms on the bottom surfaces of the substrates are completely scraped off. Two to three layers of the modified chlorinated rubber antifouling paint (which is prepared by grinding and mixing chlorinated rubber, plasticizer, cuprous oxide, pigment, adjuvant, etc.) are applied on the bottom surfaces of the substrates, with a paint film of 50-75 μm in thickness. Afterwards, the substrates were dried in the sun for one month. The substrates are returned back to the original sites in the sea.

The present invention provides the following benefits.

Aurelia spp. polyps can be significantly removed, and the reattachment of Aurelia spp. planulae on the substrates can be inhibited. Therefore, the Aurelia spp. blooms are effectively controlled. The present invention is suitable for prevention and control of Aurelia spp. blooms in harbors, providing a new technique for controlling the Aurelia spp. blooms.

In the past, the Aurelia spp. blooms were controlled by fishing, pumping and blocking with related devices. These emergency measures cost too much, and have to be carried out repeatedly every year because they are incapable of resolving the Aurelia spp. blooms entirely. Based on the life history of Aurelia spp. in basal biology and ecological principle, attachment characteristics of Aurelia spp. polyps in the natural waters, as the engine of Aurelia spp. blooms, are explored using scuba diving; therefore, the present invention solves the problem from the benthic stage, Aurelia spp polyps.

The antifouling paint is applied to the bottom surfaces of substrates after the Aurelia spp. polyps are removed. In this way, reattachment of planulae on the substrates can be inhibited. Though regular maintenance, for example, applying antifouling paint every 4 years to clear away the Aurelia spp. polyps, Aurelia spp. blooms can be effectively prevented and controlled for a long time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an image of an Aurelia coerulea ephyra.

FIG. 2 shows an image of an Aurelia coerulea polyp.

FIG. 3 shows the attachment of Aurelia spp. polyps on the bottom surfaces of floating substrates; where A is a longitudinal diagram of the substrates, and B is a sectional view of the bottom surfaces of the substrates.

FIG. 4 shows the Aurelia coerulea polyps attaching to the bottom surfaces of floating docks 1, 2, and 3.

FIG. 5 shows the Aurelia coerulea polyps attaching to sessile organisms on the bottom of the floating docks 1, 2, and 3.

FIG. 6 shows the attachment of sessile organisms on the bottom surface of the floating dock 1 in Middle Harbor (Qingdao, China) two years after the bottom surface has been painted with the antifouling paint.

FIG. 7 shows the attachment of sessile organisms on the bottom surface of the floating dock 2 in Middle Harbor (Qingdao, China) one year after the bottom surface has not been painted with the antifouling paint.

FIG. 8 shows the attachment of the Aurelia coerulea polyps on the bottom surface of the floating dock 3 without any treatment in June 2017.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The present invention is further described below with reference to the drawings and embodiments. The present invention is suitable for prevention and control of Aurelia spp. blooms in an enclosed or semi-enclosed harbor or bay, and particularly for control of aggregations of Aurelia spp. near the cooling water intakes of power plants and nuclear power plants, etc., which can significantly reduce the abundance of Aurelia spp. in nearby waters, ensuring ecological health in the harbor and safety of cooling water source of coastal infrastructures. The present invention puts forward a new technique for the control of the Aurelia spp. blooms in harbors.

Example

Taking the control of A. coerulea blooms in Middle Harbor, Port of Qingdao as an example, this embodiment is described in detail.

(1) Seeking Out A. coerulea Ephyrae in the Harbor

Massive A. coerulea appeared in the Middle Harbor, Port of Qingdao before 2014. In May 2014, five sites were designed, and Aurelia spp. ephyrae were collected with an I-type trawl net for zooplankton from bottom to surface. Massive A. coerulea ephyrae were collected in each site (3-10 ind/net, see FIG. 1). Thus, it was determined that a large number of A. coerulea polyps lived in this area. A. coerulea ephyra is mostly dark red or brown, with a cross-shaped central mouth, 8 pairs of rhopalial lappets and 8 rhopaliums. The rhopalial lappets are long and sharp without branches. Two rhopalial lappets get together at top. Nematocysts are dispersed on an umbrella surface in an irregular manner. The size of ephyrae is usually 2-3 mm.

(2) Seeking Out A. coerulea Polyps Using Scuba Diving

In June 2014, A. coerulea polyps were sought in this area by scuba diving and massive A. coerulea polyps attaching to three floating docks 1, 2, and 3 were found with a density of 2339.42±617.73 ind·m⁻². Each floating dock was approximately 30 meters in length and 8 meters in width. The A. coerulea polyp (see FIG. 2) in an obconical shape is milky white with a relatively short stalk and 16 tentacles. On the surfaces of tentacles, nematocyst cluster is distributed with obvious protruding cilia. The diameter of polyp calyx is approximately 700˜1100 μm. A. coerulea polyps settled upside down on the bottom surfaces (located 1.8 m below seawater surface) of the floating docks 1, 2, and 3, and distributed in patches (see FIG. 4). Lots of A. coerulea polyps also attached to the surfaces of some sessile organisms, such as ascidians and mussels that settled on the bottom surfaces of the floating docks (see FIG. 5).

(3) Removing A. coerulea Polyps on the Bottom Surfaces of the Substrates

In April, 2015 and 2016, the floating docks 1 and 2 were transported to Hongdao Shipyard, Jiaozhou Bay to completely scrape off A. coerulea polyps and other sessile organisms attaching to the bottom surfaces of the substrates. The floating dock 3 without treatment is provided as a control.

(4) Applying an Antifouling Paint on the Bottom Surface of the Substrate

The bottom surface of the floating dock 1 was dried in the sun for more than 7 days after the A. coerulea polyps and other sessile organisms were completely scraped off. Two layers of the modified chlorinated rubber antifouling paint, which was prepared by grinding and mixing chlorinated rubber, plasticizer, cuprous oxide, pigment, adjuvant, etc. (available from Yantai Federal Chemical Co., Ltd.), were applied on the bottom surfaces of the floating dock 1, with a paint film of 50-75 μm in thickness. The bottom surface of the floating dock 2 was dried after the A. coerulea polyps were scraped off, but not painted with the antifouling paint, in order to demonstrate the inhibition of antifouling paint against the reattachment of A. coerulea planulae. Afterwards, the floating docks 1 and 2 were dried in the sun for one month and then returned back to the original sites in the sea.

(5) Result

It was demonstrated that the abundance of A. coerulea was decreased by 66˜81% from 2015 to 2018 in comparison to 2014 using the method of the invention. Two years after the bottom surface of floating dock 1 was painted with the antifouling paint, only a small amount of sessile organisms (FIG. 6) attached to the bottom surface, and the reattachment of A. coerulea polyps were not found there. However, a large number of sessile organisms had settled on the bottom surface of the floating dock 2 without the antifouling paint one year later (FIG. 7). Lots of A. coerulea polyps appeared in the second year, the density of which was 3512.31±2229.78 ind·m⁻² in September, and more than in 2014. For the floating dock 3, massive A. coerulea polyps still settled on the empty space (left view in FIG. 8) and sessile organisms of the bottom surface (right view in FIG. 8), and the density was approximately 1700 ind·m⁻² in June (see FIG. 8). The attachment of A. coerulea polyps and other sessile organisms can be effectively inhibited by painting the antifouling paint. The A. coerulea blooms in Middle Harbor (Qingdao) can be effectively prevented and controlled for a long time through regular maintenance once every four years. 

What is claimed is:
 1. A method for controlling an Aurelia spp. bloom in a harbor, comprising: 1) designing different sites (≤10) at equal intervals in an area to be in spring, collecting Aurelia spp. ephyrae with an I-type trawl net for zooplankton from bottom to surface, determining whether Aurelia spp. polyps inhabit in the vicinity of the sites; 2) seeking large floating substrates that the polyps attach to using scuba diving in the determined habitats of the polyps; 3) dragging the substrate to a shore base and scraping off all organisms attached to bottom surfaces of the substrates in a physical manner, then air drying the substrates for more than 7 days; and 4) applying an antifouling paint to the bottom surfaces of the dried substrates followed by drying, then returning the substrates back to original sites in the sea to control the bloom of Aurelia spp. in the area.
 2. The method of claim 1, wherein in step 1), different sites (≤10) are designed at equal intervals in the area in spring (from April to May). The Aurelia app. ephyrae are collected with the I-type trawl net for zooplankton from bottom to surface to determine whether the Aurelia spp. polyps inhabit in the vicinity of the sites; if Aurelia spp. ephyrae are found in a certain site, then the polyps habitat near the site; if no ephyrae are found in this area, the area is further expanded till the Aurelia spp. ephyrae are found.
 3. The method of claim 1, wherein in step 2), the Aurelia spp. polyps are sought using a scuba diving in an area with reduced water flow near the site where Aurelia spp. ephyrae are found.
 4. The method of claim 1, wherein in step 3), all organisms attaching to the bottom surfaces of the floating substrates with polyps attached thereto are completely scraped off in a physical manner, and then the scraped substrates are dried in the sun for more than 7 days.
 5. The method of claim 1, wherein in step 4), 2-3 layers of the antifouling paint are applied on the bottom surfaces of the substrates, with a paint film of 50-75 μm in thickness. 